1. Field of the Invention
The present invention relates to a printing substrate for a liquid crystal display and a manufacturing method thereof.
2. Discussion of the Related Art
FIG. 1 is a view for illustrating a related art resist printing method.
In the resist printing method of FIG. 1, a photo resist pattern P2 is not directly transcribed from a first transparent insulating substrate 110, on which a printing pattern is patterned to be used as a printing substrate, onto a second transparent insulating substrate 120, an object to be printed, but instead, the photo resist pattern P2 is first transferred to a blanket 100 whose surface is made of silicon rubber and the like and which serves as a medium, and then is transcribed using the second insulating substrate 120 as an object to be transcribed.
FIGS. 2 through 7 illustrate the respective steps of a method of manufacturing the printing substrate as shown in FIG. 1. FIG. 2 shows the step of depositing a metal layer 111 on the transparent insulating substrate 110, FIG. 3 shows the step of applying a photo resist 112 to pattern the metal layer 111, FIG. 4 shows the step of etching the metal layer 111 using a wet eching, FIG. 5 shows the step of striping the photo resist 112, FIG. 6 shows the step of forming the printing pattern P1 by etching the first transparent insulating substrate 110, and FIG. 7 shows the step of etching and striping the metal layer 111.
In FIG. 2, because the metal layer 111 is used as a mask when the first transparent insulating substrate 110 is etched in the step illustrated in FIG. 6, the metal layer is made of a material with a tolerance to etchants used to etch the first transparent insulating substrate 110, such as Cr, Mo, etc.
As such, since the wet etching has an isotropic etching property which shows a uniform etching property without respect to the direction of crystal faces, loss to critical dimension (CD) greatly occurs due to a collective wet etching upon forming the printing pattern P1, and thus this makes it difficult to manufacture a precise printing substrate having minute patterns formed thereon.
On the contrary, a dry etching performs an etching through the acceleration force and chemical action of ions in a plasma state using a mixed chemical gas, Ar or the like. Therefore, the dry etching has an anisotropic etching property, whereas the wet etching has the isotropic etching property since it is performed in the chemical solution.
Referring to FIGS. 4 and 6, it is an ideal case that the printing pattern P1 on the first transparent insulating substrate 110 is formed to have an exact width of d1. However, if the printing substrate is manufactured through the wet etching, loss in thickness occurs on both sides of the printing substrate by the factor of d2. As an example, a printing substrate manufactured through the wet etching is theoretically impossible to implement the minimum critical dimension having less than 10 μm with respect to its both sides due to its isotropic etching property in a case where the depth of etching is 5 μm.
That is, as the printing pattern P1 has its narrower width and deeper depth, and greater ratio of depth to width, its printing property becomes better. However, the related art method using the wet etching causes the width to be broadened as the depth increases, and thus is disadvantageous to manufacture a printing substrate with minute patterns, thereby making it difficult to improve pattern resolution and transcription property.